This invention relates generally to ablative type heat shielding and more particularly to a window for such shielding.
In space and other vehicles utilizing ablative heat shielding, it is frequently necessary to transmit and receive information and data via radio frequency instruments aboard the vehicle. These antennas must be provided with a window which will allow them to function while still maintaining the integrity of the heat shielding. Without such window, electromagnetic radiation to and from the antenna would be greatly impeded or blocked by the high density ablation heat shield.
Varying density in the heat shield by the incorporation of windows or other devices necessarily tends to vary the ablation rate of the shield and in particular in those areas where substitute materials are used. In regions of varying ablation rates, material loss along the interface is severe and hence steps must be taken to prevent failure of the heat shield.
One approach, to solve the problem of severe local material loss due to differences in ablation rates, has been the incorporation of a thicker end grain heat shield collar around the periphery of the window to allow extensive trailing edge ablation. This method has advantages with regard to the trailing edge but fails to correct deficiencies in the forward edge interface. Additionally, the collar is difficult to assemble in the heat shield and increases its cost.